This paper proposes an analytical model to investigate the impact of interference on the uplink capacity and coverage in a WCDMA network where macrocell and femtocells co-exist. Geometric modeling for the hierarchical system is used where the randomly deployed femtocells are within the planned macrocells' topology. The interference effects among femtocells and between femtocells and macrocells are studied analytically to quantify the system capacity and coverage based on the practical target signal-to-interference ratio (SIR). Interference level splitting results show that the macrocell attached User Equipment (UE) to Home Node B (HNB) interference has severe impact on the capacity and coverage of femtocell network. Further study suggests that advanced receivers which cancel interference at the femtocell could minimize the effect brought by different interferences in a cost-effective manner.